What are routing select rules for and when/how would one use them?
Is there any documentation on routing select rules?
/routing filter select-rule
The help site (https://help.mikrotik.com/docs/display/ROS/Route+Selection+and+Filters#RouteSelectionandFilters-RouteSelection) does not provide enough information to explain this feature and there appear to be many options for select rules that are listed in the CLI and winbox which I can not find any references to online.
you will find out when you need them LOL.
Describe the requirements you have and the design will fall out gracefully
a. identify users/devices
b. identify the traffic they require
c. provde network diagram detailing devices being used, internet connections and intended subnet usage.
Well, you kinda need to be using some dynamic routing protocol like BGP/OSPF/RIP — but details like how any rule is invoked is missing as a starting point in the docs. Specifically both the rule and select-rule are invoked via the BGP/OSPF/RIP configuration. Standing alone /routing/filter do nothing without some initial trigger elsewhere.
I point this out since “dynamic-in” chain support from V6 was dropped, so I know what protocols you can use router filters, since I lost “dynamic” one from V6 
. e.g. in V7, you cannot do some “if ( afi ipv4 ) { set gw-check icmp; accept }” for a route added by DHCP client – while this was possible in V6 — which avoided the scripting in /ip/dhcp-client to set check-gateway=ping required in V7.
OP is correct that “select-rule” is pretty skimpy on docs… While this is true and covers the “why”:
By default, (if no selection rules are set) output always picks the best route. […] But there might be cases > where you would want preference for other routes, not the active ones> , and here come in-play selection rules.
…there is no explanation of the options in docs, or how/when to invoke/use them on the BGP/OSPF side.
I have a complex BGP setup with many peers and many filters.
It seems that routing select rules may be able to help, simplify my setup, but since most of them seem to be undocumented, I can’t make use of them, which is why I was asking about the documentation.
If anyone knows the correct way to use them, and how the various options work, I’d like to know.
Route Selection is still a mystery?